the rust can be safely removed, but the pitting can be permanent if it is deep enough.
to remove the rust, a little 0000 steel wool and a bit of oil is all you need. The bluing, what is left of it, will be fine

__________________Hundreds of years from now, it will not matter what my bank account was, the sort of house I lived in, or the kind of car I drove... But the world may be different because I did something so bafflingly crazy that my ruins become a tourist attraction.